1. Field of the Invention
The present invention generally relates to film deposition apparatuses, substrate processing apparatuses, film deposition methods and storage media, and more particularly to a film deposition apparatus, a substrate processing apparatus and a film deposition method for forming a thin film by alternately supplying at least two kinds of source gases, and to a computer-readable storage medium which stores a program which, when executed by a computer, causes the computer to execute such a film deposition method.
2. Description of the Related Art
As a film deposition method of a semiconductor fabrication (or manufacturing) process, there is a known process which causes a first reaction gas to adsorb on a surface of a semiconductor wafer (hereinafter simply referred to as a “wafer”), which is used as a substrate, under a vacuum environment, and thereafter switches the gas that is supplied to a second reaction gas, in order to form one or a plurality of atomic or molecular layers using the reaction of the two gases. Such a deposition cycle is performed a plurality of times to stack and deposit the layers on the substrate. This known process is referred to as the Atomic Layer Deposition (ALD) or Molecular Layer Deposition (MLD). According to this known process, the film thickness can be controlled with a high accuracy depending on the number of cycles performed, and a satisfactory in-plane uniformity of the film quality can be achieved. Therefore, this known process is a promising technique that can cope with further reduced film thicknesses of semiconductor devices.
Such a film deposition method may be used to deposit a dielectric film having a high dielectric constant for use as a gate oxide film, for example. When silicon dioxide (SiO2) is deposited as the gate oxide film, a bis(tertiary-butylamino)silane (BTBAS) gas or the like is used as a first reaction gas (source gas) and an ozone gas or the like is used as a second gas (oxidation gas).
In order to carry out such a film deposition method, the use of a single-wafer deposition apparatus having a vacuum chamber and a shower head at a top center portion of the vacuum chamber has been under consideration. In such a film deposition apparatus, the reaction gases are introduced into the chamber from the top center portion, and unreacted gases and by-products are evacuated from a bottom portion of the chamber. When such a deposition chamber is used, it takes a long time for a purge gas to purge the reaction gases, resulting in an extremely long process time because the number of cycles may reach several hundred. Therefore, a film deposition method and a film deposition apparatus that can achieve a high throughput are desired.
Under these circumstances, film deposition apparatuses having a vacuum chamber and a turntable that holds a plurality of wafers along a rotating direction have been proposed.
A U.S. Pat. No. 7,153,542 proposes a film deposition apparatus with a vacuum chamber which has a flat cylinder shape and is divided into right and left areas. Each of the right and left areas has an evacuation port which is formed along a semi-circular contour thereof and is provides upward evacuation. In addition, a separation area formed with a gas inlet port for introducing a separation gas is provided between the right semi-circular contour and the left semi-circular contour, that is, at a diametrical area of the vacuum chamber. Supply areas for mutually different source gases are formed in the right semi-circular area and the left semi-circular area. A work piece passes through the right semi-circular area, the separation area, and the left semi-circular area by rotating a turntable within the vacuum chamber, and the source gases are evacuated via the evacuation port. A ceiling of the separation area to which the separation gas is supplied is lower that that of the supply areas to which the source gases are supplied.
A Japanese Laid-Open Patent Publication No. 2001-254181 proposes a film deposition apparatus in which four wafers are arranged at equal distances on a wafer support member (turntable) along the rotating direction. First and second reaction gas ejection nozzles are arranged at equal distances along the rotating direction in order to oppose the wafer support member. Purge nozzles are arranged between the first and the second gas ejection nozzles. The wafer support member is rotated horizontally. Each wafer is supported by the wafer support member, and an upper surface of the wafer is higher than an upper surface of the wafer support member by an amount corresponding to the thickness of the wafer. The distance between the nozzles and the wafer is 0.1 mm or greater. Vacuum evacuation is made from between the outer edge of the wafer support member and the inner wall of the process chamber. According to this film deposition apparatus, a so-called air curtain is generated below the purge gas nozzles, to thereby prevent the first and second reaction gases from being mixed.
A Japanese Patent No. 3144664 proposes a film deposition apparatus with vacuum chamber that is divided into a plurality of process chambers along the circumferential direction by a plurality of partitions. A circular rotatable susceptor on which a plurality of wafers are placed is provided below the partitions, with a slight gap between the susceptor and the partitions.
A Japanese Laid-Open Patent Publication No. 4-287912 proposes a film deposition method which divides a circular gas supply plate into 8 sections in the circumferential direction, and arranges a AsH3 gas supply port, a H2 gas supply port, a TMG gas supply port and a H2 gas supply port at 90 degree intervals. Further, evacuation ports are provided between the gas supply ports. A susceptor which supports a wafer and opposes the gas supply plate is rotated.
A U.S. Pat. No. 6,634,314 proposes a film deposition apparatus in which an upper area of a turntable is divided into four quarters by four partition walls, and a wafers is placed in each of the four partitioned areas. A source gas injector, a reaction gas injector, and a purge gas injector are alternately arranged in the rotating direction in order to form a cross-shaped injector unit. The injector unit is rotated horizontally so that the injectors sequentially oppose the four partitioned areas, and a vacuum evacuation is made from a periphery of the turntable.
A Japanese Laid-Open Patent Publication No. 2007-247066 proposes a film deposition apparatus for an atomic layer Chemical Vapor Deposition (CVD) that causes a plurality of gases to be alternately adsorbed on a target (corresponding to a wafer). In this apparatus, a susceptor that holds the wafer is rotated, while source gases and purge gases are supplied from above the susceptor. Paragraphs 0023 to 0025 of the Japanese Laid-Open Patent Publication No. 2007-247066 describe partition walls that extend in a radial direction from a center of a chamber, and gas ejection holes that are provided below the partition walls in order to supply the source gases or the purge gas to the susceptor, so that an inert gas is ejected from gas ejection holes to generate a gas curtain. Regarding evacuation of the gases, paragraph 0058 of the Japanese Laid-Open Patent Publication No. 2007-247066 describes that the source and purge gases are evacuated separately through respective evacuation channels 30a and 30b. Techniques similar to that proposed in the Japanese Laid-Open Patent Publication No. 2007-247066 are also proposed in U.S. Patent Application Publications No. US2007/0218701 and No. US2007/0218702.
However, the following problems are encountered when a film deposition process is performed using the film deposition apparatus or the film deposition method proposed in the eight patent documents described above, by arranging a plurality of substrates on the turntable within the vacuum chamber in the rotating direction.
According to the film deposition apparatus and the film deposition method proposed in the U.S. Pat. No. 7,153,542, the upward evacuation port is provided between the separation gas ejection hole and the reaction gas supply area, and the reaction gas is evacuated from the evacuation port together with the separation gas. For this reason, the reaction gas ejected onto the work piece forms an upward flow and is sucked into the evacuation port, to thereby blow particles upwards which may contaminate the wafer.
According to the film deposition apparatus and the film deposition method proposed in the Japanese Laid-Open Patent Publication No. 2001-254181, the air curtain generated from the purge gas nozzles cannot prevent mixture of the reaction gases and may allow the reaction gases on both sides particularly from the upstream side of the rotating direction to flow through the air curtain, because the wafer support member rotates. In addition, the first reaction gas discharged from the first gas outlet nozzle may flow through the center portion of the wafer support member corresponding to the turntable and reach the second reaction gas discharged from the second gas outlet nozzle. If the first reaction gas and the second reaction gas mixed above the wafer, a reaction product is adsorbed on the wafer surface, and it becomes difficult to perform a satisfactory ALD (or MLD) process.
According to the film deposition apparatus and the film deposition method proposed in the Japanese Patent No. 3144664, the process gas may diffuse into the adjacent process chamber from the gap between the partition and the susceptor or the wafer. In addition, because an evacuation chamber is provided between a plurality of process chambers, the gases from the process chambers on the upstream side and the downstream side mix into the evacuation chamber when the wafer passes through the evacuation chamber. Accordingly, the film deposition technique employing the ALD cannot be applied to the proposed film deposition apparatus and the proposed film deposition method.
According to the film deposition apparatus and the film deposition method proposed in the Japanese Laid-Open Patent Publication No. 4-287912, no realistic means is proposed on how to separate the two reaction gases, and the two reaction gases will mix not only in a vicinity of the center of the susceptor but will actually also mix in a region other than the vicinity of the center of the susceptor where the H2 gas supply port is arranged. In addition, when the evacuation port is provided in a surface opposing the region where the wafer passes, the wafer is easily contaminated by the particles that are blown upwards from the susceptor surface.
According to the film deposition apparatus and the film deposition method proposed in the U.S. Pat. No. 6,634,314, after the source gas or the reaction gas is supplied to each partitioned area, it takes a long time to flush the environment of the partitioned area by the purge gas from the purge gas nozzle. Moreover, the source gas or the reaction gas may diffuse from one partitioned area to an adjacent partitioned area by riding over a vertical wall, and the two gases may react in the partitioned area.
According to the film deposition apparatus and the film deposition method proposed in the Japanese Laid-Open Patent Publication No. 2007-247066, the U.S. Patent Application Publication No. US2007/0218701 or the U.S. Patent Application Publication No. US2007/0218702, the source gases may flow into a purge gas compartment from source gas compartments located on both sides of the purge gas compartment and become mixed with each other in the purge gas compartment. As a result, a reaction product is generated in the purge gas compartment, which may cause particles to contaminate the wafer.
Furthermore, according to the film deposition apparatuses and the film deposition methods proposed in the U.S. Pat. No. 7,153,542, the Japanese Laid-Open Patent Publication No. 2001-254181, the Japanese Patent No. 3144664, the Japanese Laid-Open Patent Publication No. 4-287912 and the U.S. Pat. No. 6,634,314, when the film deposition is performed by supplying a corrosive reaction gas including Cl or the like as the first reaction gas or, when a corrosive cleaning gas including Cl or the like is supplied after the film deposition from the nozzle which supplies the first reaction gas, corrosion of portions made of an aluminum material, such as the ceiling of the vacuum chamber, occurs.